Can i colour part of the same 3D text which was converted from 2D text. ( Convert mesh to curve )
You could use a Gradient and a ColorRamp node to change the color along the curve. That said, I don't know how you can make the gradient follow the curve, someone may have an answer, here I kept the gradient horizontal.



And of course, you could convert your curve to mesh, in that case use a b&amp;w mask as a factor in a Mix shader to go from a color to another one:


Convert your mesh to curve, unwrap it with the Smart UV Project mode.
Give it an Image Texture node. Paint it in black and white. It will be the mask that will separate your 2 colors.
Now organize your nodes, plug the b&amp;w picture in the factor of your Mix shader.




Another solution would be to parent a straight mesh pipe to bones (maybe with a Spline IK constraint) then twist the bones the way you want (or the curve in the case of a Spline IK), the texture will follow.